Methods of simultaneously cleaning and disinfecting industrial water systems

ABSTRACT

On-Line and Off-Line methods of simultaneously cleaning and disinfecting an industrial water system are described and claimed. The methods involve the addition to the water of the industrial water system of a Compound selected from the group consisting of the alkali salts of chlorite and chlorate and mixtures thereof; and an acid, followed by allowing the water in the industrial water system to circulate for several hours. The reaction of the alkali salts of chlorite and chlorate and acid produces chlorine dioxide in-situ in the water of the industrial water system. The chlorine dioxide kills microorganisms and the acid acts to remove deposits upon the water-contact surfaces of the equipment. An alternative method involves the use of a chelating agent and a biocide. Other possible cleaning and disinfection reagents may be added as needed including corrosion inhibitors, chelating agents, biocides, surfactants and reducing agents. These cleaning and disinfecting methods work in a variety of industrial water systems including cooling water and boiler water systems.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

[0001] This patent application is a continuation-in-part of U.S. patentapplication Ser. No. 10/135,317, filed Apr. 30, 2002, now pending.

FIELD OF THE INVENTION

[0002] This invention is in the field of industrial water systems.Specifically, this invention is in the field of cleaning anddisinfection of industrial water systems.

BACKGROUND OF THE INVENTION

[0003] Throughout the world, there are many different types ofindustrial water systems. Industrial water systems exist so thatnecessary chemical, mechanical and biological processes can be conductedto reach the desired outcome. Fouling can occur even in industrial watersystems treated with the best water treatment programs currentlyavailable. For purposes of this patent application “fouling” is definedas “the deposition of any organic or inorganic material on a surface”.

[0004] If these industrial water systems are not periodically cleaned,then they will become heavily fouled. Fouling has a negative impact onthe industrial water system. For example, severe mineral scale(inorganic material) will buildup on the water contact surfaces andanywhere there is scale, there is an ideal environment for the growth ofmicroorganisms.

[0005] Evaporative cooling water systems are particularly prone tofouling. This fouling occurs by a variety of mechanisms includingdeposition of air-borne and waterborne and water-formed contaminants,water stagnation, process leaks, and other factors. If allowed toprogress, the system can suffer from decreased operational efficiency,premature equipment failure, and increased health-related risksassociated with microbial fouling.

[0006] Fouling can also occur due to microbiological contamination.Sources of microbial contamination in industrial water systems arenumerous and may include, but are not limited to, air-bornecontamination, water make-up, process leaks and improperly cleanedequipment. These microorganisms can establish microbial communities onany wetable or semi-wetable surface of the water system. Once thesemicrobial populations are present in the bulk water more than 99% of themicrobes present in the water will be present on all surfaces.

[0007] Exopolymeric substance secreted by microorganisms aid in theformation of biofilms as the microbial communities develop on thesurface. These biofilms are complex ecosystems that establish a meansfor concentrating nutrients and offer protection for growth, andbiofilms can accelerate scale, corrosion, and other fouling processes.Not only do biofilms contribute to reduction of system efficiencies, butthey also provide an excellent environment for microbial proliferationthat can include Legionella bacteria. It is therefore important thatbiofilms and other fouling processes be reduced to the greatest extentpossible to minimize the health-related risk associated with Legionellaand other water-borne pathogens.

[0008] There are several different cleaning or disinfection methods forcooling water systems. For example, mechanical cleaning,hyperhalogenation with and without surfactants or dispersants, and acidcleaning, are amongst the cleaning methods most commonly used.

[0009] A simple mechanical cleaning program consists of “power washing”and “scrubbing”. Power washing refers to the use of high-pressure waterdirected at equipment surfaces such that the impact of the water on thesurface removes deposits from those surfaces that can be reached.Mechanical cleaning strategies do not always remove all heavily adheringdeposits such as deposited scale and biological slime from equipmentsurfaces. Further limitations on the use of mechanical cleaning includethe fact that such methods are effective at removing only loosedeposits, and not for removing deposits from within the fill (in thecase of a cooling tower). For systems such as domestic waterdistribution pipes, power washing is completely ineffective. Mechanicalcleaning methods also do not provide a means of disinfection, which iscrucial to maintaining clean and safe equipment.

[0010] One standard procedure that uses hyperhalogenation and surfactantis commonly known as the “Wisconsin Protocol”, see “CONTROL OFLEGIONELLA IN COOLING TOWERS”, Summary Guidelines, Section of Acute andCommunicable Disease Epidemiology, Bureau of Community Health andPrevention, Division of Health, Wisconsin Department of Health andSocial Services, August 1987. The Wisconsin Protocol is used todisinfect an industrial water system following a Legionellosis outbreak.Even in the absence of an outbreak, hyperhalogenation is commonly usedto reduce microbial fouling in water systems. Hyperhalogenationprotocols do not remove mineral scale, thereby limiting their ability toremove or reduce biological foulants. In addition, the hyperhalogenationprocedures that require a biodispersant have limited effectivenesswithin the period the protocol is implemented. The use of certain acids,such as sulfuric acid, in combination with high halogen doses, asspecified in the Wisconsin Protocol, can form copper sulfate and otherdeposits that are subsequently difficult to remove. Finally, because thehyperhalogenation methods do not remove scale and other depositssufficiently, microbial populations re-establish rapidly in the systems.

[0011] An “acid cleaning procedure” is designed to remove mineral scale.Acid is capable of removing alkaline scale from virtually all wetablesurfaces. Acid cleaning procedures offer limited disinfection because ofthe lowered pH, but do not adequately penetrate biological deposits(biofilms) that remain associated with system surfaces.

[0012] Operators of industrial water systems use chlorine dioxide tokill microorganisms. Chlorine dioxide is a well-known biocide, but doesnot have the ability to remove mineral scale. Chlorine dioxide must begenerated on-site where it is applied. There are several methods forgenerating and delivering chlorine dioxide. One of these methods usesacid in combination with sodium chlorite (acid activation). For example,the chlorine dioxide is generated using sodium chlorite and hydrochloricacid as follows:

5 NaClO₂+4 HCl=4 ClO₂+5 NaCl+2 H₂O

[0013] Typically, the reactants (sodium chlorite and hydrochloric acid)are mixed and allowed to react to form chlorine dioxide. Following thisreaction, the products (chlorine dioxide, sodium chloride, water, someremaining unreacted sodium chlorite, and hydrochloric acid) are addeddirectly into the water of the industrial water system. Once thisexternally-generated chlorine dioxide solution is applied to the watersystem, the chlorine dioxide is diluted and either lost throughvolatility or is reduced by substances within the water system. Usingthis method, chlorine dioxide must be constantly generated outside thewater system, and injected into the system to maintain a chlorinedioxide residual.

[0014] Patent Cooperation Treaty Patent Application WO 02/12130 A1describes and claims a method of treating water in a water distributionsystem, comprising:

[0015] admixing a sodium chlorite solution with a second solutioncontaining an acid to make a reacted mixture; and

[0016] introducing a predetermined amount of the reacted mixture into awater system.

[0017] As described in this Patent Cooperation Treaty PatentApplication, the preferred method of treating water includes theaddition of a catalyst, wherein the catalyst is sodium molybdate.

[0018] United Kingdom Patent Application No. 2,313,369 describes andclaims an aqueous composition having a pH of more than 9 consists of astabilized chlorine dioxide precursor, an alkali metal polyphosphate andan alkali metal hydroxide. It also describes and claims a method oftreating water in a water distribution system comprising the addition ofan acid activator to the aqueous composition to reduce the pH to lessthan 7 and injecting the aqueous solution in to the water system.

[0019] It would be desirable to have a method for simultaneouslycleaning and disinfecting an industrial water system.

SUMMARY OF THE INVENTION

[0020] The first aspect of the instant claimed invention is a method ofsimultaneously cleaning and disinfecting an industrial water systemcomprising the steps of:

[0021] a) providing an industrial water system;

[0022] b) adding to the water of said industrial water system

[0023] i) a Compound, wherein said Compound is selected from the groupconsisting of the alkali salts of chlorite and chlorate, or a mixturethereof; and

[0024] ii) an acid;

[0025] wherein said acid is added before the Compound is added; and

[0026] c) allowing the water to circulate through the industrial watersystem for at least from about one to about 72 hours; and

[0027] d) draining the water from the industrial water system.

[0028] The second aspect of the instant claimed invention is a method ofsimultaneously cleaning and disinfecting an industrial water systemcomprising the steps of:

[0029] a) providing an industrial water system;

[0030] b) adding to the water of said industrial water system

[0031] i) a Compound, wherein said Compound is selected from the groupconsisting of the alkali salts of chlorite and chlorate, or a mixturethereof; and

[0032] ii) an acid;

[0033] wherein said Compound is added before the acid is added; and

[0034] c) allowing the water to circulate through the industrial watersystem for at least from about one to about 72 hours; and

[0035] d) draining the water from the industrial water system.

[0036] The third aspect of the instant claimed invention is an on-linemethod of simultaneously cleaning and disinfecting an industrial watersystem comprising the steps of:

[0037] a) providing an industrial water system; wherein said industrialwater system is selected from the group consisting of cooling watersystems and boiler water systems;

[0038] b) optionally reducing the cycles of said industrial water systemto single cycles and halting the feeding of the routine watermaintenance chemicals to the water of the industrial water system;

[0039] c) adding a Compound selected from the group consisting of thealkali salts of chlorite and chlorate, or a mixture thereof, andoptionally adding a corrosion inhibitor and optionally adding adispersant to the water of said industrial water system; wherein enoughCompound is added to reach a concentration of from about 1 ppm to about1000 ppm; wherein if a corrosion inhibitor is added enough corrosioninhibitor is added to reach a concentration of from about 50 ppm toabout 500 ppm and wherein if a dispersant is added enough dispersant isadded to reach a concentration of from about 1 ppm to about 500 ppm;

[0040] d) lowering the pH of the water in the industrial water system toabout 4.0 by adding an acid to the water of said industrial water systemand maintaining the pH of the water in the industrial water system atabout 4.0 for from about 1 to about 4 hours;

[0041] e) adding a chelating agent to the water of the industrial watersystem, wherein enough chelating agent is added to maintain theconcentration of the chelating agent at from about 10 ppm to about 500ppm in the water of the industrial water system; wherein said chelatingagent is added either before or after the next step of raising the pH;

[0042] f) optionally raising the pH of the water in the industrial watersystem from about 5.5 to about 11 by either adding caustic or stoppingthe addition of acid or by a combination of both of these methods;

[0043] g) adding a biocide to the water of the industrial water system;wherein if the chelating agent is added after the optional step ofraising the pH, then the chelating agent and the biocide from step g)may be added simultaneously to the water or the chelating agent may beadded first followed by the biocide or the biocide may be added first,followed by the chelating agent; wherein the amount of biocide added isthat amount sufficient to have a concentration of from about 1 ppm toabout 500 ppm in the water of the industrial water system;

[0044] h) allowing the water in the industrial water system to circulatefor an additional time period of from about 1 hour to about 120 hours;and

[0045] i) concluding the cleaning and disinfecting method when thedesired cleaning efficiency has been achieved; wherein, if feeding ofthe routine water treatment maintenance chemicals was stopped during theprocess, then now resuming the feeding of the routine water treatmentmaintenance chemicals to the water of the industrial water system; andwherein if feeding of the routine water treatment maintenance chemicalswas not stopped during the procedure, then now bringing the industrialwater system back to normal operation by stopping cleaning chemicalfeed, blowing down the water to reduce system cycles to a single cycle,and then proceeding under normal operating conditions.

[0046] The fourth aspect of the instant claimed invention is:

[0047] an on-line method of simultaneously cleaning and disinfecting anindustrial water system comprising the steps of:

[0048] a) providing an industrial water system; wherein said industrialwater system is selected from the group consisting of cooling watersystems and boiler water systems;

[0049] b) optionally reducing the cycles of said industrial water systemto single cycles and halting the feeding of the routine watermaintenance chemicals to the water of the industrial water system.

[0050] c) adding a chelating agent to the water of the industrial watersystem, wherein enough chelating agent is added to maintain theconcentration of the chelating agent at from about 10 ppm to about 500ppm in the water of the industrial water system; wherein said chelatingagent is added either before or after the optional next step ofmaintaining the pH;

[0051] d) optionally maintaining the pH of the water in the industrialwater system from about 5.5 to about 11 by either adding caustic orstopping the addition of acid or by a combination of both of thesemethods;

[0052] e) adding a biocide to the water of the industrial water system;wherein if the chelating agent is added after the optional step ofmaintaining the pH, then the chelating agent and the biocide from stepe) may be added simultaneously to the water or the chelating agent maybe added first followed by the biocide or the biocide may be addedfirst, followed by the chelating agent; wherein the amount of biocideadded is that amount sufficient to have a concentration of from about 1ppm to about 500 ppm in the water of the industrial water system;

[0053] f) allowing the water in the industrial water system to circulatefor an additional time period of from about 1 hour to about 120 hours;and

[0054] g) concluding the cleaning and disinfecting method when thedesired cleaning efficiency has been achieved; wherein, if feeding ofthe routine water treatment maintenance chemicals was stopped during theprocess, then now resuming the feeding of the routine water treatmentmaintenance chemicals to the water of the industrial water system; andwherein if feeding of the routine water treatment maintenance chemicalswas not stopped during the procedure, then now bringing the industrialwater system back to normal operation by stopping cleaning chemicalfeed, blowing down the water to reduce system cycles to a single cycle,and then proceeding under normal operating conditions.

DETAILED DESCRIPTION OF THE INVENTION

[0055] Throughout this patent application, the following terms have thestated meaning

[0056] “Fouling” refers to the deposition of any organic or inorganicmaterial on a surface. These deposits impede water flow and/or heattransfer, and harbor microorganisms that cause increased deposition,enhance corrosion and increase health-related risks.

[0057] “Cleaning” means reducing the overall quantity of deposits, whichis desirable because reducing the overall quantity of deposits improvesthe overall efficiency of the industrial water system.

[0058] “Disinfection” is typically used to describe a method for killingmicroorganisms. As used herein, the goal of disinfection is to cause anoverall significant reduction in the number or viability ofmicroorganisms within the water system.

[0059] “ONC” refers to Ondeo Nalco Company, Ondeo Nalco Center, 1601 W.Diehl Road, Naperville, Ill. 60563, telephone (630) 305-1000.

[0060] The first and second aspects of the instant claimed invention area method of simultaneously cleaning and disinfecting an industrial watersystem comprising the steps of:

[0061] a) providing an industrial water system;

[0062] b) adding to the water of said industrial water system

[0063] i) a Compound selected from the group consisting of the alkalisalts of chlorite and chlorate or a mixture thereof; and

[0064] ii) an acid; and

[0065] wherein said acid is added before the Compound is added, or theacid is added after the Compound is added;

[0066] c) allowing the water to circulate through the industrial watersystem for at least from about one to about 72 hours; and

[0067] d) draining the water from the industrial water system.

[0068] The method of the instant claimed invention can be used tosimultaneously clean and disinfect industrial water systems that arebeing installed, those that are currently in operation, are temporarilynot operating, or have been inactive for extended periods and are beingrestored to service.

[0069] The method of the instant claimed invention can be used to cleanand disinfect many industrial water systems. These industrial watersystems include, but are not limited to cooling water systems, includingopen recirculating, closed and once-through cooling water systems;boilers and boiler water systems; petroleum wells, downhole formations,geothermal wells and other oil field applications; mineral processwaters including mineral washing, flotation and benefaction; paper milldigesters, washers, bleach plants, stock chests, and white watersystems, and paper machine surfaces; black liquor evaporators in thepulp industry; gas scrubbers and air washers; continuous castingprocesses in the metallurgical industry; air conditioning andrefrigeration systems; industrial and petroleum process water; indirectcontact cooling and heating water, such as pasteurization water; waterreclamation systems, water purification systems; membrane filtrationwater systems; food processing streams (meat, vegetable, sugar beets,sugar cane, grain, poultry, fruit and soybean); and waste treatmentsystems as well as in clarifiers, liquid-solid applications, municipalsewage treatment, municipal water systems, potable water systems,aquifers, water tanks, sprinkler systems and water heaters. Thepreferred industrial water systems to be simultaneously cleaned anddisinfected by the method of the instant claimed invention are coolingwater systems, including open recirculating, closed and once-throughcooling water systems, paper machine surfaces, food processing streams,waste treatment systems and potable water systems. The most preferredindustrial water systems to be simultaneously cleaned and disinfected bythe method of the instant claimed invention are cooling water systems,including open recirculating, closed and once-through cooling watersystems.

[0070] Prior to conducting the method of the instant claimed inventionit is typically recommended, though not required, that the addition ofany chemical or biological treatment chemicals to the water bediscontinued. It is also recommended to stop all energy transfer withinthe system so that prior to addition of the Compound and acid, the waterof the industrial water system is circulating through the industrialwater system without being chemically or biologically treated andwithout having heat transfer occurring.

[0071] The Compound is selected from the alkali salts of chlorite andchlorate and mixtures thereof. These alkali salts include sodiumchlorite, potassium chlorite, sodium chlorate and potassium chlorate.The preferred alkali salts are sodium chlorite and sodium chlorate. Themost preferred alkali salt is sodium chlorite.

[0072] The alkali salts of chlorite and chlorate are commodity chemicalsthat can be obtained from most chemical supply companies. Sodiumchlorite can be obtained either at its normal pH or in its colloquiallyreferred to “stabilized form” at an elevated pH. The preferred sodiumchlorite is a 25% solution of sodium chlorite in water. This material isavailable as HYG-25 from ONC.

[0073] Sodium chlorate is a commodity chemical that can be obtained frommost chemical supply companies. The preferred sodium chlorate is fromabout a 20 to about a 50 Wt/Wt % solution of sodium chlorate in water.This preferred sodium chlorate is available from Eka Chemicals, Inc.,1775 West Oak Commons Court, Marietta, Ga. 30062-2254 USA, telephonenumber 1-770-578-0858.

[0074] Potassium chlorite and potassium chlorate are both available frommost chemical supply companies.

[0075] The amount of sodium chlorite or potassium chlorite added to thewater of the industrial water system depends upon what type ofindustrial water system is being cleaned and disinfected. If the methodof the instant claimed invention is applied to a cooling water system,then the amount of sodium chlorite or potassium chlorite added is fromabout 1 ppm to about 1000 ppm, preferably from about 10 ppm to about 500ppm and most preferably from about 50 ppm to about 250 ppm.

[0076] The amount of sodium chlorate or potassium chlorate added to thewater of the industrial water system depends upon what type ofindustrial water system is being cleaned and disinfected. If the methodof the instant claimed invention is applied to a cooling water system,then the amount of sodium chlorate added is from about 1 ppm to about1000 ppm, preferably from about 10 ppm to about 500 ppm and mostpreferably from about 50 ppm to about 250 ppm.

[0077] If sodium chlorite or potassium chlorite and sodium chlorate orpotassium chlorate are both used then the ratio of chlorite to chlorate,expressed in weight percent, is from about 1:99 to about 99:1,preferably from about 10:90 to about 90:10, and most preferably about50:50. The total amount of both chlorite and chlorate together is thesame as that for either chlorite or chlorate used separately.

[0078] The acid is selected from the group consisting of mineral acidsand organic acids wherein said mineral acids are selected from the groupconsisting of hydrochloric acid, sulfuric acid, amido sulfuric acid(98%), nitric acid, phosphoric acid, hydrofluoric acid and sulfamicacid; and said organic acids are selected from the group consisting ofcitric acid and its salts, formic acid, acetic acid, peracids includingperacetic acid, peroxyacetic acid and peroxyformic acid, glycolic acid(hydroxyacetic acid), oxalic acid, propionic acid, lactic acid(hydroxypropionic acid) and butyric acid. The choice of acid dependsprimarily upon metallurgy within the system. For metals such as carbonsteel, copper or yellow metal alloys the preferred acids arehydrochloric acid, sulfamic acid, formic acid and glycolic acid. Themost preferred acid, for most metals, is hydrochloric acid.

[0079] These acids are commercial chemicals available from a chemicalsupply company. These acids can be purchased in dry or in liquid form orin formulations that contain other functional chemicals which also canbe in dry or liquid form. For instance, most of these acids can beobtained in formulation with corrosion inhibitors. Hydrochloric acidformulated with a corrosion inhibitor made of diethyl urea is sold asNalco®2560 Inhibited HCl by ONC.

[0080] The amount of acid added to the water of the industrial watersystem depends upon what type of industrial water system is beingcleaned and disinfected. If the method of the instant claimed inventionis applied to a cooling water system, then the amount of acid added isthat required to achieve and maintain a pH from about 1 to about 5,preferably from about 1 to about 3 and most preferably from about 2 toabout 2.5. People of ordinary skill in the art know how to calculate howmuch of each acid would be required in order to achieve the desired pHby taking into account the system volume and the alkalinity within thesystem.

[0081] The Compound that is selected from the group consisting of thealkali salts of chlorite and chlorate and mixtures thereof and the acidare added directly to the water of the industrial water system, withoutbeing premixed prior to addition. Either the acid is added before theCompound or the Compound is added before the acid. It is possible,although not preferred, to add the acid and Compound simultaneously tothe water.

[0082] The advantage of the instant claimed method is that it ispossible to obtain continuous generation of chlorine dioxidedisinfectant throughout the water system while also achievingsimultaneous acid cleaning. Adding the Compound and the acid separatelyallows a certain amount of circulation of the Compound and acid prior totheir reaction to create chlorine dioxide. This means more chlorinedioxide is created farther away from the point of addition of theCompound and the acid.

[0083] After the Compound and acid are added to the water, the water isallowed to circulate throughout the industrial water system. Thiscirculation of water allows the cleaning and disinfection of the“water-contact” surfaces of equipment in the industrial water system. Inaddition to the cleaning and disinfection of the water contact surfaces,volatile chlorine dioxide is also capable of reaching surfaces that arenot continuously in contact with water.

[0084] The water in the industrial water system is allowed to circulatefor a time period of from about 1 hour to about 72 hours, preferablyfrom about 1 hour to about 24 hours and most preferably from about 1hour to about 8 hours.

[0085] During these time periods it is possible, though not required, tomonitor the progress of the cleaning and {indirectly monitor}disinfection by using standard techniques to determine the amount ofions present in the water due to the breaking up and detachment ofinorganic deposits. The inorganic deposits are typically calcium salts,magnesium salts, iron oxide, copper oxide and manganese salts. Forinstance, it is known that it is typical for the amount of calcium ionin the water to rise steadily as the cleaning progresses and scale,known to contain calcium, is detached from the surfaces of theequipment. When the amount of calcium in the water plateaus it indicatesthat the cleaning is complete because no new calcium scale is beingdissolved.

[0086] After the cleaning and disinfection is finished, the water in theindustrial water system must be drained and sent for appropriatetreatment so that it can be discharged in compliance with state andlocal regulations. Of course, once the water is drained, it may benecessary to conduct additional mechanical cleaning of the water contactsurfaces. This mechanical cleaning is recommended when the cleaning anddisinfection has worked so well that there is an accumulation of loosedirt and other undesired material collected in the nooks and crannys ofthe industrial water system. These nooks and crannys can include thefill used in most cooling towers. After mechanical cleaning is over, itis possible to refill the water and begin operation of the industrialwater system. For heavily contaminated industrial water systems it isalso possible to fill the industrial water system with water and conductthe method of the instant claimed invention again.

[0087] In addition to the chemicals named, it is possible to conduct themethod of the instant claimed invention by adding additional functionalchemicals. These additional functional chemicals include additionalbiocides, corrosion inhibitors, dispersants, surfactants, reducingagents and chemicals added for pH adjustment.

[0088] Additional biocides can be added when microbial contamination issevere. Biocides suitable for use in the instant claimed invention areselected from the group consisting of oxidizing or non-oxidizingbiocides. Oxidizing biocides include, but are not limited to, chlorinebleach, chlorine, bromine and materials capable of releasing chlorineand bromine. The preferred oxidizing biocide is chlorine bleach.Non-oxidizing biocides include, but are not limited to, glutaraldehyde,isothiazolin, 2,2-dibromo-3-nitrilopropionamide,2-bromo-2-nitropropane-1,3 diol,1-bromo-1-(bromomethyl)-1,3-propanedicarbonitrile,tetrachloroisophthalonitrile, alkyldimethylbenzylammonium chloride,dimethyl dialkyl ammonium chloride, didecyl dimethyl ammonium chloride,poly(oxyethylene(dimethyliminio)ethylene(dimethyliminio)ethylenedichloride, methylene bisthiocyanate, 2-decylthioethanamine,tetrakishydroxymethyl phosphonium sulfate, dithiocarbamate,cyanodithioimidocarbonate, 2-methyl-5-nitroimidazole-1-ethanol,2-(2-bromo-2-nitroethenyl)furan, beta-bromo-beta-nitrostyrene,beta-nitrostyrene, beta-nitrovinyl furan, 2-bromo-2-bromomethylglutaronitrile, bis(trichloromethyl) sulfone,S-(2-hydroxypropyl)thiomethanesulfonate,tetrahydro-3,5-dimethyl-2H-1,3,5-hydrazine-2-thione,2-(thiocyanomethylthio)benzothiazole, 2-bromo-4′-hydroxyacetophenone,1,4-bis(bromoacetoxy)-2-butene, bis(tributyltin)oxide,2-(tert-butylamino)-4-chloro-6-(ethylamino)-s-triazine, dodecylguanidineacetate, dodecylguanidine hydrochloride, coco alkyldimethylamine oxide,n-coco alkyltrimethylenediamine, tetra-alkyl phosphonium chloride,7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid,4,5-dichloro-2-n-octyl-4-isothiazoline3-one,5-chloro-2-methyl-4-isothiazolin-3-one and2-methyl-4-isothiazolin-3-one. The preferred non-oxidizing biocide is2,2-dibromo-3-nitrilopropionamide and is available from ONC.

[0089] If the method of the instant claimed invention is applied to acooling water system, then the amount of oxidizing biocide added is fromabout 0.1 ppm to about 200 ppm, preferably from about 1 ppm to about 100ppm, more preferably from about 5 to about 50 ppm and most preferablyfrom about 5 ppm to about 20 ppm.

[0090] Corrosion inhibitors can be added when needed to reduce corrosionof the metal in the industrial water system. Corrosion inhibitors formulti-metal protection are typically triazoles, such as, but not limitedto, benzotriazole, halogenated triazoles, nitro-substituted azoles, andother triazoles as listed in U.S. Pat. No. 5,874,026, which isincorporated by reference in its entirety. The preferred triazole isbenzotriazole.

[0091] Triazoles are commercially available from most chemical supplycompanies. The preferred benzotriazole is Nalco® 73199, which isavailable from Ondeo Nalco Company.

[0092] Whether a corrosion inhibitor is used depends upon the industrialwater system and the composition of the water contact surfaces in theindustrial water system. For example, if all the water contact surfacesin the industrial water system are wood, noble metals, glass, titaniumor plastic, then the use of corrosion inhibitor in those systems is notindicated. However, when the water contact surfaces are non-titaniummetal, such as, but not limited to, stainless steel, carbon steel,galvanized steel, and yellow metals such as copper, admiralty and brass,then the use of a corrosion inhibitor is preferred.

[0093] The amount of corrosion inhibitor added to the water of theindustrial water system depends upon what type of industrial watersystem is being cleaned and disinfected. If the method of the instantclaimed invention is applied to a cooling water system, then the amountof corrosion inhibitor added is from about 1 ppm to about 2000 ppm,preferably from about 10 ppm to about 1000 ppm and most preferably fromabout 50 ppm to about 600 ppm.

[0094] The corrosion inhibitor may be added before, after or during theaddition of the Compound and the acid. The corrosion inhibitor ispreferably added prior to the addition of acid. The corrosion inhibitorcan be added immediately before the acid and Compound are added.However, it is preferred that the corrosion inhibitor be addedsufficiently in advance of the addition of acid that the corrosioninhibitor can circulate throughout the system. Thus it is preferred thatthe corrosion inhibitor be added from about 1 hour to about 24 hoursprior to addition of the Compound and acid.

[0095] The corrosion inhibitor could also be preformulated with otheringredients being added to the water. As mentioned previously, corrosioninhibitor can be formulated with acid to create an “inhibited acid”.

[0096] Dispersants are added when needed to keep particulate matterpresent in the water of an industrial water system dispersed, so that itdoes not agglomerate and cause fouling during the cleaning anddisinfecting process. Dispersants are typically low molecular weightanionic polymers, with “low” referring to a weight average molecularweight of from about 500 to about 20,000. These polymers are typically,but not limited to acrylic acid, polymaleic acid, copolymers of acrylicacid with sulfonated monomers and alkyl esters thereof. These polymerscan include terpolymers of acrylic acid, acrylamide and sulfonatedmonomers. These polymers can also include quad-polymers consisting ofacrylic acid and three other monomers.

[0097] Dispersant polymers are commercially available from most chemicalsupply companies. The preferred dispersant polymer is a High StressPolymer such as High Stress Polymer PR 4832 which is available fromOndeo Nalco Company.

[0098] Whether a dispersant is used depends upon the industrial watersystem, the deposits present in the system and the foulants present inthe water and the composition of the water contact surfaces in theindustrial water system.

[0099] The amount of dispersant added to the water of the industrialwater system depends upon what type of industrial water system is beingcleaned and disinfected. If the method of the instant claimed inventionis applied to a cooling water system then the amount of dispersant addedis from about 1 ppm to about 500 ppm, preferably from about 5 ppm toabout 200 ppm and most preferably from about 10 ppm to about 100 ppm.

[0100] The dispersant may be added before, after or during the additionof the Compound and the acid. The dispersant could also be preformulatedwith other ingredients being added to the water.

[0101] One or more surfactants may be added when and where needed toenhance the cleaning and disinfection process. Surfactants useful inindustrial water systems include, but are not limited to, ethylene oxidepropylene oxide copolymers, linear alkylbenzene sulfonates (“LAS”),ethoxylated phosphate esters, and alkyl polyglycosides, and othersurfactants described in U.S. Pat. No. 6,139,830, U.S. Pat. No.5,670,055 and U.S. Pat. No. 6,080,323, which are all incorporated byreference.

[0102] Surfactants are commercially available from most chemical supplycompanies. The preferred surfactants are ethylene oxide propylene oxidecopolymers and alkyl polyglycosides. These surfactants CL-103, CL-361,CL-362, Nalco®73550, and Nalco®7348 are available from ONC.

[0103] Whether a surfactant is used depends upon the industrial watersystem, the deposit or foulant, and the composition of the water contactsurfaces in the industrial water system.

[0104] The amount of surfactant added to the water of the industrialwater system depends upon what type of industrial water system is beingcleaned and disinfected. If the method of the instant claimed inventionis applied to a cooling water system, then the amount of surfactantadded is from about 0.1 ppm to about 1000 ppm, preferably from about 1ppm to about 500 ppm and most preferably from about 5 ppm to about 100ppm.

[0105] Surfactant could be added at any time during the method ofsimultaneous cleaning and disinfection, but surfactant would preferablybe added after chlorine dioxide generation has started {in order toreduce any potential aerosolization of viable microbial foulants}.

[0106] One or more reducing agents may be added when and where needed toreact with oxidants present in order to prepare the water for dischargein compliance with state and local environmental regulations. Reducingagents suitable for use in the method of the instant claimed inventioninclude, but are not limited to, sodium thiosulfate, sodium bisulfite,sodium metabisulfite and sodium sulfite.

[0107] Reducing agents such as these are commercially available frommost chemical supply companies. The preferred reducing agent is sodiumbisulfite which is available from Ondeo Nalco Company.

[0108] Whether a reducing agent is used depends upon the industrialwater system and the amount of oxidants present therein. The amount ofreducing agent added to the water of the industrial water system dependsupon what type of industrial water system is being cleaned anddisinfected. If the method of the instant claimed invention is appliedto a cooling water system, then the amount of reducing agent added isequimolar to the amount of oxidant present. Another way of determiningthe amount of reducing agent that is required is to add reducing agentuntil there is no residual halogen present.

[0109] The reducing agent is typically added at the conclusion of thecleaning and disinfection process just before the water is to bedischarged or may be added to the discharge pipe or reservoir.

[0110] A pH adjusting chemical may be added when needed to adjust the pHof the water being discharged from the industrial water system. TypicalpH adjusting chemicals include, but are not limited to, NaOH (aka“caustic”), KOH, Ca(OH)₂, Na₂CO₃ and K₂CO₃. The preferred pH adjustingchemical is caustic, specifically a 50% solution of NaOH in water.Caustic is commercially available from most chemical supply companies.

[0111] The amount of pH adjusting chemical added to the water of theindustrial water system depends upon what type of industrial watersystem is being cleaned and disinfected, what the pH of the watertypically is and what are the pH requirements for the water beingdischarged from the industrial water system.

[0112] If the method of the instant claimed invention is applied to acooling water system, then the amount of pH adjusting chemical added isthat required to achieve a pH from about 2 to about 8, preferably fromabout 3 to about 7 and most preferably from about 4 to about 6. The pHadjusting chemical is typically added at the conclusion of the cleaningand disinfection process just before the water is to be discharged or itmay be added to the discharge pipe or reservoir.

[0113] In practicing the method of the instant claimed invention all ofthe chemicals may be added separately. Aside from the Compound and acidbeing added separately, the other chemicals may be formulated together.

[0114] A preferred formulation would include corrosion inhibitor,dispersant and surfactant blended together in a single product.

[0115] At the conclusion of the process, the water containing thecleaning and disinfection chemicals and residual material removed fromthe water is drained from the industrial water system. Then, the systemcan be refilled with water and returned to service right away or not,depending on the needs of the system operators. It is of course possibleto fill the tower with fresh water and conduct the method of the instantclaimed invention again, in order to clean heavily contaminatedindustrial water systems.

[0116] If a cooling tower has been cleaned and disinfected by the methodof the instant claimed invention, any of the following actions can takeplace at the conclusion of the method.

[0117] 1) fill the cooling tower using fresh make-up water, and begindosing a “normal” treatment program of inhibitors and biocides;

[0118] 2) fill the cooling tower using fresh make-up water, and begindosing a program of inhibitors and/or biocides at elevated doses, toachieve passivation of any exposed metals and kill off any remainingorganisms, followed by resumption of a “normal” treatment program;

[0119] 3) leave the cooling tower dry during a period in which coolingis not required; or fill the system with fresh make-up water, and slugdose inhibitors and/or biocide at elevated doses, then drain the system(without ever having resumed normal function) and leave dry during aperiod in which cooling is not required.

[0120] 4) fill the cooling tower with fresh make-up water, drain thesystem and refill, slug dose inhibitors and/or biocide at elevated ornormal doses, then return to service.

[0121] The advantages of the first and second aspects of the instantclaimed invention include the fact that this cleaning and disinfectionprocedure removes deposits from virtually all wetable surfaces, andsimultaneously disinfects bulk water and all wetable surfaces, and somesurfaces not continually in contact with the water, by in-situgeneration of ClO₂. The method of the instant claimed invention isdesigned to minimize corrosion while cleaning and disinfection aretaking place, can be completed in less than eight hours, effectivelyremoves microbial deposits and significantly extends the period formicrobial re-colonization. The procedure works well to clean heavilyfouled industrial water systems.

[0122] The third aspect of the instant claimed invention is an on-linemethod of simultaneously cleaning and disinfecting an industrial watersystem comprising the steps of:

[0123] a) providing an industrial water system; wherein said industrialwater system is selected from the group consisting of cooling watersystems and boiler water systems;

[0124] b) optionally reducing the cycles of said industrial water systemto single cycles and halting the feeding of the routine watermaintenance chemicals to the water of the industrial water system;

[0125] c) adding a Compound selected from the group consisting of thealkali salts of chlorite and chlorate, or a mixture thereof, andoptionally adding a corrosion inhibitor and optionally adding adispersant to the water of said industrial water system; wherein enoughCompound is added to reach a concentration of from about 1 ppm to about1000 ppm; wherein if a corrosion inhibitor is added enough corrosioninhibitor is added to reach a concentration of from about 50 ppm toabout 500 ppm and wherein if a dispersant is added enough dispersant isadded to reach a concentration of from about 1 ppm to about 500 ppm;

[0126] d) lowering the pH of the water in the industrial water system toabout 4.0 by adding an acid to the water of said industrial water systemand maintaining the pH of the water in the industrial water system atabout 4.0 for from about 1 to about 4 hours;

[0127] e) adding a chelating agent to the water of the industrial watersystem, wherein enough chelating agent is added to maintain theconcentration of the chelating agent at from about 10 ppm to about 500ppm in the water of the industrial water system; wherein said chelatingagent is added either before or after the next step of raising the pH;

[0128] f) optionally raising the pH of the water in the industrial watersystem from about 5.5 to about 11 by either adding caustic or stoppingthe addition of acid or by a combination of both of these methods;

[0129] g) adding a biocide to the water of the industrial water system;wherein if the chelating agent is added after the step of raising thepH, then the chelating agent and the biocide from step g) may be addedsimultaneously to the water or the chelating agent may be added firstfollowed by the biocide or the biocide may be added first, followed bythe chelating agent; wherein the amount of biocide added is that amountsufficient to have a concentration of from about 1 ppm to about 500 ppmin the water of the industrial water system;

[0130] h) allowing the water in the industrial water system to circulatefor an additional time period of from about 1 hour to about 120 hours;and

[0131] i) concluding the cleaning and disinfecting method when thedesired cleaning efficiency has been achieved; wherein, if feeding ofthe routine water treatment maintenance chemicals was stopped during theprocess, then now resuming the feeding of the routine water treatmentmaintenance chemicals to the water of the industrial water system; andwherein if feeding of the routine water treatment maintenance chemicalswas not stopped during the procedure, then now bringing the industrialwater system back to normal operation by stopping the cleaning chemicalfeed, blowing down the water to reduce system cycles to a single cycle,and then proceeding under normal operating conditions.

[0132] The third aspect of the instant claimed invention is a methodapplicable to cooling water systems and boiler water systems. Theseindustrial water systems consist of evaporative cooling towers, openre-circulating, closed and once-through cooling water systems; boilersand boiler water systems and industrial water systems including coolingwater equipment and boiler equipment.

[0133] The Compound is selected from the alkali salts of chlorite andchlorate and mixtures thereof. These alkali salts include sodiumchlorite, potassium chlorite, sodium chlorate and potassium chlorate.The preferred alkali salts are sodium chlorite and sodium chlorate. Themost preferred alkali salt is sodium chlorite.

[0134] The alkali salts of chlorite and chlorate are commodity chemicalsthat can be obtained from most chemical supply companies. Sodiumchlorite can be obtained either at its normal pH or in its colloquiallyreferred to “stabilized form” at an elevated pH. The preferred sodiumchlorite is a 25% solution of sodium chlorite in water. This material isavailable as HYG-25 from ONC.

[0135] Sodium chlorate is a commodity chemical that can be obtained frommost chemical supply companies. The preferred sodium chlorate is fromabout a 20 to about a 50 Wt/Wt % solution of sodium chlorate in water.This preferred sodium chlorate is available from Eka Chemicals, Inc.,1775 West Oak Commons Court, Marietta, Ga. 30062-2254 USA, telephonenumber 1-770-578-0858.

[0136] Potassium chlorite and potassium chlorate are both available frommost chemical supply companies.

[0137] The amount of sodium chlorite or potassium chlorite added to thewater of the industrial water system depends upon what type ofindustrial water system is being cleaned and disinfected. If the methodof the instant claimed invention is applied to a cooling water system,then the amount of sodium chlorite or potassium chlorite added is fromabout 1 ppm to about 1000 ppm, preferably from about 10 ppm to about 500ppm, most preferably from about 50 ppm to about 250 ppm and most highlypreferably about 100 ppm.

[0138] If sodium chlorite or potassium chlorite and sodium chlorate orpotassium chlorate are both used then the ratio of chlorite to chlorate,expressed in weight percent, is from about 1:99 to about 99:1,preferably from about 10:90 to about 90:10, and most preferably about50:50. The total amount of both chlorite and chlorate together is thesame as that for either chlorite or chlorate used separately.

[0139] The corrosion inhibitor optionally used in the third aspect ofthe instant claimed invention is selected from the group consisting ofbenzotriazole, halogenated triazoles, nitro-substituted azole, and thetriazoles listed in U.S. Pat. No. 5,874,026, which is incorporated byreference in its entirety. The preferred triazole is benzotriazole.Benzotriazole is available from ONC as Nalco 73199. The amount of azoleadded is that amount sufficient to reach a concentration of about 50 toabout 500 ppm in the water of the industrial water system. The preferredconcentration of azole is about 100 ppm in the water of the industrialwater system.

[0140] The dispersant optionally used in the third aspect of the instantclaimed invention is selected from the group consisting of, but notlimited to, High Stress Polymer (as previously described), acrylic acid,polymaleic acid, copolymers of acrylic acid with sulfonated monomers andalkyl esters thereof. These polymeric dispersants can includeterpolymers of acrylic acid, acrylamide and sulfonated monomers. Thesepolymeric dispersants can also include quad-polymers consisting ofacrylic acid and three other monomers. The preferred dispersant is aterpolymer comprising from about 30-70 mol % acrylic acid, from about10-30 mol % Acrylamide and from about 20-40 mol % aminomethylsulfonicacid. A terpolymer with such composition is available from ONC as HighStress Polymer PR 4382.

[0141] The amount of dispersant added is that amount sufficient to reacha concentration of from about 1 ppm to about 500 ppm. The preferredamount of dispersant is about 100 ppm.

[0142] The acid used in the third aspect of the instant claimedinvention is either a mineral acid or an organic acid selected from thegroup consisting of hydrochloric acid, sulfuric acid, amido sulfuricacid (98%), nitric acid, phosphoric acid, hydrofluoric acid and sulfamicacid; and said organic acids are selected from the group consisting ofcitric acid and its salts, formic acid, acetic acid, peracids includingperacetic acid, peroxyacetic acid and peroxyformic acid, glycolic acid(hydroxyacetic acid), oxalic acid, propionic acid, lactic acid(hydroxypropionic acid) and butyric acid. The preferred acid is glycolicacid, which is available as Nalco R3076 from ONC. The amount of acidadded is that amount sufficient to lower the pH of the water to about4.0 and subsequently to maintain the pH at about 4.0.

[0143] The chelating agent useful in the third aspect of the instantclaimed invention is selected from the group consisting of sodiumhexametaphosphate, sodium polyphosphate, phosphonates, andpolycarboxylates (homopolymers and copolymers). The preferred chelatingagent is sodium hexametaphosphate. It is available as Glassy Calgon fromONC. Sufficient chelating agent is added such that the concentration ofthe chelating agent at from about 10 ppm to about 500 ppm in the waterof the industrial water system.

[0144] The biocide useful in the third aspect of the instant claimedinvention can be an oxidizing biocide or a non-oxidizing biocide.Oxidizing biocides are selected from the group consisting of chlorinebleach, chlorine, bromine and materials capable of releasing chlorineand bromine. The preferred oxidizing biocide is chlorine bleach.Non-oxidizing biocides are selected from the group consisting ofglutaraldehyde, isothiazolin, 2,2-dibromo-3-nitrilopropionamide,2-bromo-2-nitropropane-1,3 diol,1-bromo-1-(bromomethyl)-1,3-propanedicarbonitrile,tetrachloroisophthalonitrile, alkyldimethylbenzylammonium chloride,dimethyl dialkyl ammonium chloride, didecyl dimethyl ammonium chloride,poly(oxyethylene(dimethyliminio)ethylene(dimethyliminio)ethylenedichloride, methylene bisthiocyanate, 2-decylthioethanamine,tetrakishydroxymethyl phosphonium sulfate, dithiocarbamate,cyanodithioimidocarbonate, 2-methyl-5-nitroimidazole-1-ethanol,2-(2-bromo-2-nitroethenyl)furan, beta-bromo-beta-nitrostyrene,beta-nitrostyrene, beta-nitrovinyl furan, 2-bromo-2-bromomethylglutaronitrile, bis(trichloromethyl) sulfone,S-(2-hydroxypropyl)thiomethanesulfonate,tetrahydro-3,5-dimethyl-2H-1,3,5-hydrazine-2-thione,2-(thiocyanomethylthio)benzothiazole, 2-bromo-4′-hydroxyacetophenone,1,4-bis(bromoacetoxy)-2-butene, bis(tributyltin)oxide,2-(tert-butylamino)-4-chloro-6-(ethylamino)-s-triazine, dodecylguanidineacetate, dodecylguanidine hydrochloride, coco alkyldimethylamine oxide,n-coco alkyltrimethylenediamine, tetra-alkyl phosphonium chloride,7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid,4,5-dichloro-2-n-octyl-4-isothiazoline-3-one,5-chloro-2-methyl-4-isothiazolin-3-one and2-methyl-4-isothiazolin-3-one, The preferred non-oxidizing biocide is2,2-dibromo-3-nitrilopropionamide, which is available as Nalco N7649from ONC. The amount of biocide added is that amount sufficient to havea concentration of from about 1 ppm to about 20 ppm in the water of theindustrial water system.

[0145] In the third aspect of the instant claimed invention, the on-linemethod of cleaning and disinfection of industrial water systems allowsfor cleaning of inorganic and organic deposits initially through loweredpH, using an acid for a short period of time and subsequently for aprolonged period of time using a chelating agent at a near neutral pH.The disinfection takes place initially through the in-situ generation ofchlorine dioxide when the pH is about 4.0, followed by addition of achelating agent and a biocide when the pH is near neutral.

[0146] The fourth aspect of the instant claimed invention is: an on-linemethod of simultaneously cleaning and disinfecting an industrial watersystem comprising the steps of:

[0147] a) providing an industrial water system; wherein said industrialwater system is selected from the group consisting of cooling watersystems and boiler water systems;

[0148] b) optionally reducing the cycles of said industrial water systemto single cycles and halting the feeding of the routine watermaintenance chemicals to the water of the industrial water system.

[0149] c) adding a chelating agent to the water of the industrial watersystem, wherein enough chelating agent is added to maintain theconcentration of the chelating agent at from about 10 ppm to about 500ppm in the water of the industrial water system; wherein said chelatingagent is added either before or after the optional next step ofmaintaining the pH;

[0150] d) optionally maintaining the pH of the water in the industrialwater system from about 5.5 to about 11 by either adding caustic orstopping the addition of acid or by a combination of both of thesemethods;

[0151] e) adding a biocide to the water of the industrial water system;wherein if the chelating agent is added after the optional step ofmaintaining the pH, then the chelating agent and the biocide from stepe) may be added simultaneously to the water or the chelating agent maybe added first followed by the biocide or the biocide may be addedfirst, followed by the chelating agent; wherein the amount of biocideadded is that amount sufficient to have a concentration of from about 1ppm to about 500 ppm in the water of the industrial water system;

[0152] f) allowing the water in the industrial water system to circulatefor an additional time period of from about 1 hour to about 120 hours;and

[0153] g) concluding the cleaning and disinfecting method when thedesired cleaning efficiency has been achieved; wherein, if feeding ofthe routine water treatment maintenance chemicals was stopped during theprocess, then now resuming the feeding of the routine water treatmentmaintenance chemicals to the water of the industrial water system; andwherein if feeding of the routine water treatment maintenance chemicalswas not stopped during the procedure, then now bringing the industrialwater system back to normal operation by stopping cleaning chemicalfeed, blowing down the water to reduce system cycles to a single cycle,and then proceeding under normal operating conditions.

[0154] In the fourth aspect of the instant claimed invention, cleaningis attributed to chelation by the chelating agent and the disinfectionoccurs as a function of the added biocide.

[0155] The chelating agent useful in the fourth aspect of the instantclaimed invention is selected from the group consisting of sodiumhexametaphosphate, sodium polyphosphate, phosphonates, andpolycarboxylates (homopolymers and copolymers). The preferred chelatingagent is sodium hexametaphosphate. It is available as Glassy Calgon fromONC. Sufficient chelating agent is added such that the concentration ofthe chelating agent at from about 10 ppm to about 500 ppm in the waterof the industrial water system.

[0156] The biocide useful in the fourth aspect of the instant claimedinvention can be an oxidizing biocide or a non-oxidizing biocide.Oxidizing biocides are selected from the group consisting of chlorinebleach, chlorine, bromine and materials capable of releasing chlorineand bromine. The preferred oxidizing biocide is chlorine bleach.

[0157] Non-oxidizing biocides are selected from the group consisting ofglutaraldehyde, isothiazolin, 2,2-dibromo-3-nitrilopropionamide,2-bromo-2-nitropropane-1,3 diol,1-bromo-1-(bromomethyl)-1,3-propanedicarbonitrile,tetrachloroisophthalonitrile, alkyldimethylbenzylammonium chloride,dimethyl dialkyl ammonium chloride, didecyl dimethyl ammonium chloride,poly(oxyethylene(dimethyliminio)ethylene(dimethyliminio)ethylenedichloride, methylene bisthiocyanate, 2-decylthioethanamine,tetrakishydroxymethyl phosphonium sulfate, dithiocarbamate,cyanodithioimidocarbonate, 2-methyl-5-nitroimidazole-1-ethanol,2-(2-bromo-2-nitroethenyl)furan, beta-bromo-beta-nitrostyrene,beta-nitrostyrene, beta-nitrovinyl furan, 2-bromo-2-bromomethylglutaronitrile, bis(trichloromethyl) sulfone,S-(2-hydroxypropyl)thiomethanesulfonate,tetrahydro-3,5-dimethyl-2H-1,3,5-hydrazine-2-thione,2-(thiocyanomethylthio)benzothiazole, 2-bromo-4′-hydroxyacetophenone,1,4-bis(bromoacetoxy)-2-butene, bis(tributyltin)oxide,2-(tert-butylamino)-4-chloro-6-(ethylamino)-s-triazine, dodecylguanidineacetate, dodecylguanidine hydrochloride, coco alkyldimethylamine oxide,n-coco alkyltrimethylenediamine, tetra-alkyl phosphonium chloride,7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid,4,5-dichloro-2-n-octyl-4-isothiazoline-3-one,5-chloro-2-methyl-4-isothiazolin-3-one and2-methyl-4-isothiazolin-3-one, The preferred non-oxidizing biocide is2,2-dibromo-3-nitrilopropionamide, which is available as Nalco N7649from ONC. The amount of biocide added is that amount sufficient to havea concentration of from about 1 ppm to about 500 ppm in the water of theindustrial water system.

[0158] The following examples are presented to be illustrative of thepresent invention and to teach one of ordinary skill how to make and usethe invention. These examples are not intended to limit the invention orits protection in any way.

EXAMPLES

[0159] A plastic Pilot Cooling Tower with titanium metal heat exchangersand a plastic sump is chosen as a test site for the method of the secondaspect of the instant claimed invention. The Pilot Cooling Tower is inalmost continuous use for over one year so there is severe contaminationpresent. The contamination is believed to be both inorganic scale aswell as microbiological sessile populations. There is visible fouling onmost of the water contact surfaces as well as visible particulate matterpresent in the water that is circulating.

[0160] To conduct the method of the instant claimed invention it isnecessary to take the Pilot Cooling Tower out of service for 24 hours.

[0161] To prepare for the cleaning and disinfection of the Pilot CoolingTower, the cooling system heat load is removed. The cooling system fansare turned-off and the blowdown valve is closed. The addition of watertreatment program chemicals are discontinued, such that the watercirculating through the Pilot Cooling Tower has only residual watertreatment chemicals present.

[0162] Throughout the cleaning and disinfection program, Pilot CoolingTower water recirculation remains on. Benzotriazole and the dispersant,which is High Stress Polymer PR 4832 from ONC are added to the water ofthe Pilot Cooling Tower. Enough benzotriazole is added to achieve aconcentration of about 100 ppm. Enough High Stress Polymer is added toachieve a concentration of about 100 ppm.

[0163] Sufficient sodium chlorite (NaClO₂), taken from the chemicalstockroom, is added to the system water such that its concentration inthe water is 100 ppm. The sodium chlorite is circulated in the systemfor 30 minutes.

[0164] Inhibited hydrochloric acid is then added to the water.Sufficient hydrochloric acid is added such that the pH of the water isfrom about 2.0 to about 3.0, preferably about 2.5. The water iscirculated for 6 hours while continuing to add whatever acid is requiredin order to maintain a pH of from about 2.0 to about 2.5. Duringcleaning and disinfection, samples are periodically collected andmonitored for chlorine dioxide using standard analytical technique todetermine chlorine dioxide {such as the diethyl-p-phenylene diamine test(“the DPD test”) for free residual chlorine dioxide, expressed “aschlorine”} as well as determining the level of hardness present bycomplexometric titration.

[0165] During this six hour time period, chlorine dioxide concentrationsare found to be in the range of from about 0.5 to about 1.0 ppm,expressed as free chlorine. Hardness values increase from 600 to 2000ppm over a 5 hour period. After 5 hours, the hardness value increasesare minimal and acid addition is stopped. The system water isrecirculated for one additional hour. The system is drained. The systemis flushed with fresh makeup water and drained a second time.

[0166] A visual inspection of the water contact surfaces shows cleansurfaces with no contamination. The method of simultaneous cleaning anddisinfection is deemed to be a success.

[0167] After the second drainage, the Pilot Cooling Tower is refilledwith fresh makeup water and returned to normal service.

Example 2

[0168] This is an example of the third aspect of the instant claimedinvention.

[0169] A plastic Pilot Cooling Tower with titanium metal heat exchangersand a plastic sump is chosen as a test site for the method of the thirdaspect of the instant claimed invention. The Pilot Cooling Tower is inalmost continuous use so there is severe contamination present. Thecontamination is believed to be both inorganic scale as well asmicrobiological sessile populations. There is visible fouling on most ofthe water contact surfaces as well as visible particulate matter presentin the water that is circulating.

[0170] To prepare for the cleaning and disinfection of the Pilot CoolingTower, the cooling system water is blown-down to reduce system water tosingle cycle. The heat load and the cooling system fans is maintained inoperation. For this example, the addition of water treatment programchemicals is discontinued, such that the water circulating through thePilot Cooling Tower has only residual water treatment chemicals present.

[0171] Throughout the cleaning and disinfection program, Pilot CoolingTower water re-circulation remains on. Benzotriazole and the dispersant,which is High Stress Polymer PR 4832 from ONC are added to the water ofthe Pilot Cooling Tower. Enough benzotriazole is added to achieve aconcentration of about 100 ppm. Enough High Stress Polymer is added toachieve a concentration of about 100 ppm.

[0172] Sufficient sodium chlorite (NaClO₂), taken from the chemicalstockroom, is added to the system water such that its concentration inthe water is 100 ppm. The sodium chlorite is circulated in the systemfor 30 minutes.

[0173] Glycolic acid is then added to the water. Sufficient glycolicacid is added such that the pH of the water is from about 3.5 to about5.5, preferably about 4.0. The water is circulated for about 1.0 toabout 4.0 hours, preferably about 2.0, while continuing to add whateveracid is required in order to maintain a pH of from about 4.0 to about4.25. During cleaning and disinfection, samples are periodicallycollected and monitored for chlorine dioxide using standard analyticaltechnique to determine chlorine dioxide {such as the diethyl-p-phenylenediamine test (“the DPD test”) for free residual chlorine dioxide,expressed “as chlorine”} as well as determining the level of hardnesspresent by complexometric titration.

[0174] During this two hour time period, chlorine dioxide concentrationsare found to be in the range of from about 0.5 to about 1.0 ppm,expressed as free chlorine. Hardness values increase from 400 to 1600ppm over a 2 hour period. After 2 hours, the acid feed is stopped andthe system water pH is allowed to rise due to the increasing alkalinitywithin the system. A rapid rise in the pH is also achieved by theaddition of enough caustic solution to bring the pH to about 5.0 to 6.5,preferably 5.5.

[0175] Sufficient sodium hexametaphosphate, used as a chelating agent,taken from the Ondeo Nalco chemical stockroom, is added to the systemwater such that its concentration in the water is from about 10 ppm toabout 500 ppm, preferably 200 ppm.

[0176] Sufficient quantities of a non-oxidizing biocide2,2-dibromo-3-nitrilopropionamide, taken from the Ondeo Nalco chemicalstockroom, is added to the system water such that its concentration inthe water is from about 1 ppm to about 20 ppm.

[0177] The system water pH is maintained at 5.5 with intermittentaddition of glycolic acid, as needed. The system water blow-down wasmaintained per normal operational program and loss of chemical (sodiumhexametaphosphate and 2,2-dibromo-3-nitrilopropionamide) following blowdown was replenished by slug doses of the chemicals. The system water isrecirculated for a period of about 48 hours. The total hardness levelsare monitored periodically and when hardness level increases areminimal, the acid and biocide feed is stopped and the cleaning processis deemed completed. The system water is blown down to single cycles,and the routine water treatment program is reinstated. The industrialwater system is returned to normal service.

[0178] A visual inspection of the water contact surfaces shows cleansurfaces with no contamination. The method of on-line simultaneouscleaning and disinfection is deemed to be a success.

What is claimed is:
 1. A method of simultaneously cleaning anddisinfecting an industrial water system comprising the steps of: a)providing an industrial water system; b) adding to the water of saidindustrial water system i) a Compound, wherein said Compound is selectedfrom the group consisting of the alkali salts of chlorite and chlorateand mixtures thereof; and ii) an acid; and  wherein said acid is addedbefore the Compound is added; c) allowing the water to circulate throughthe industrial water system for at least from about one to about 72hours; and d) draining the water from the industrial water system. 2.The method of claim 1 wherein said industrial water system is selectedfrom the group consisting of cooling water systems, including openrecirculating, closed and once-through cooling water systems; boilersand boiler water systems; petroleum wells, downhole formations,geothermal wells and other oil field applications; mineral processwaters including mineral washing, flotation and benefaction; paper milldigesters, washers, bleach plants, stock chests, and white watersystems, and paper machine surfaces; black liquor evaporators in thepulp industry; gas scrubbers and air washers; continuous castingprocesses in the metallurgical industry; air conditioning andrefrigeration systems; industrial and petroleum process water; indirectcontact cooling and heating water, such as pasteurization water; waterreclamation systems, water purification systems, membrane filtrationwater systems; food processing streams (meat, vegetable, sugar beets,sugar cane, grain, poultry, fruit and soybean); and waste treatmentsystems as well as in clarifiers, liquid-solid applications, municipalsewage treatment, municipal water systems, potable water systems,aquifers, water tanks, sprinkler systems and water heaters.
 3. Themethod of claim 2 wherein said industrial water system is a coolingwater system.
 4. The method of claim 1 wherein said Compound is eithersodium chlorite, potassium chlorite or mixtures thereof.
 5. The methodof claim 1 wherein said Compound is either sodium chlorate, potassiumchlorate or mixtures thereof.
 6. The method of claim 1 wherein saidCompound is a mixture of either sodium chlorite or potassium chloriteand either sodium chlorite or potassium chlorite.
 7. The method of claim1 wherein said acid is selected from the group consisting ofhydrochloric acid, sulfuric acid, nitric acid, phosphoric acid,hydrofluoric acid, sulfamic acid, citric acid, formic acid, acetic acid,peracids including peracetic acid, peroxyacetic acid and peroxyformicacid, glycolic acid (hydroxyacetic acid), oxalic acid, propionic acid,lactic acid (hydroxypropionic acid), butyric acid and salts thereof. 8.The method of claim 7 in which said acid is hydrochloric acid.
 9. Themethod of claim 1 in which additional chemicals are added to the waterof the industrial water system, with said additional chemicals beingselected from the group consisting of biocides, corrosion inhibitors,dispersants, surfactants, reducing agents and pH adjusting chemicals.10. The method of claim 9 in which said biocides are selected from thegroup consisting of chlorine bleach, chlorine, bromine and materialscapable of releasing chlorine and bromine.
 11. The method of claim 9 inwhich said corrosion inhibitors are selected from the group consistingof triazoles.
 12. The method of claim 9 in which said dispersants areselected from the group consisting of low molecular weight anionicpolymers.
 13. The method of claim 9 in which said surfactants areselected from the group consisting of ethylene oxide propylene oxidecopolymers, linear alkylbenzene sulfonates, ethoxylated phosphate estersand alkyl polyglycosides.
 14. The method of claim 9 in which saidreducing agents are selected from the group consisting of sodiumthiosulfate, sodium bisulfite, sodium metabisulfite and sodium sulfite.15. The method of claim 9 in which said pH adjusting agents are selectedfrom the group consisting of caustic and soda ash.
 16. A method ofsimultaneously cleaning and disinfecting an industrial water systemcomprising the steps of: a) providing an industrial water system; b)adding to the water of said industrial water system i) a Compound,wherein said Compound is selected from the group consisting of thealkali salts of chlorite and chlorate and mixtures thereof; and ii) anacid; and wherein said Compound is added before the acid is added; c)allowing the water to circulate through the industrial water system forat least from about one to about 72 hours; and d) draining the waterfrom the industrial water system.
 17. The method of claim 16 whereinsaid industrial water system is selected from the group consisting ofcooling water systems, including open recirculating, closed andonce-through cooling water systems; boilers and boiler water systems;petroleum wells, downhole formations, geothermal wells and other oilfield applications; mineral process waters including mineral washing,flotation and benefaction; paper mill digesters, washers, bleach plants,stock chests, and white water systems, and paper machine surfaces; blackliquor evaporators in the pulp industry; gas scrubbers and air washers;continuous casting processes in the metallurgical industry; airconditioning and refrigeration systems; industrial and petroleum processwater; indirect contact cooling and heating water, such aspasteurization water; water reclamation systems, water purificationsystems, membrane filtration water systems; food processing streams(meat, vegetable, sugar beets, sugar cane, grain, poultry, fruit andsoybean); and waste treatment systems as well as in clarifiers,liquid-solid applications, municipal sewage treatment, municipal watersystems, potable water systems, aquifers, water tanks, sprinkler systemsand water heaters.
 18. The method of claim 17 wherein said industrialwater system is a cooling water system.
 19. The method of claim 16wherein said Compound is either sodium chlorite, potassium chlorite ormixtures thereof.
 20. The method of claim 16 wherein said Compound iseither sodium chlorate, potassium chlorate or mixtures thereof.
 21. Themethod of claim 16 wherein said Compound is a mixture of either sodiumchlorite or potassium chlorite and either sodium chlorite or potassiumchlorite.
 22. The method of claim 16 wherein said acid is selected fromthe group consisting of hydrochloric acid, sulfuric acid, nitric acid,phosphoric acid, hydrofluoric acid, sulfamic acid, citric acid, formicacid, acetic acid, peracids including peracetic acid, peroxyacetic acidand peroxyformic acid, glycolic acid (hydroxyacetic acid), oxalic acid,propionic acid, lactic acid (hydroxypropionic acid), butyric acid andsalts thereof.
 23. The method of claim 22 in which said acid ishydrochloric acid.
 24. The method of claim 16 in which additionalchemicals are added to the water of the industrial water system, withsaid additional chemicals being selected from the group consisting ofbiocides, corrosion inhibitors, dispersants, surfactants, reducingagents and pH adjusting chemicals.
 25. The method of claim 24 in whichsaid biocides are selected from the group consisting of chlorine bleach,chlorine, bromine and materials capable of releasing chlorine andbromine.
 26. The method of claim 24 in which said corrosion inhibitorsare selected from the group consisting of triazoles.
 27. The method ofclaim 24 in which said dispersants are selected from the groupconsisting of low molecular weight anionic polymers.
 28. The method ofclaim 24 in which said surfactants are selected from the groupconsisting of ethylene oxide propylene oxide copolymers, linearalkylbenzene sulfonates, ethoxylated phosphate esters and alkylpolyglycosides.
 29. The method of claim 24 in which said reducing agentsare selected from the group consisting of sodium thiosulfate, sodiumbisulfite, sodium metabisulfite and sodium sulfite.
 30. The method ofclaim 24 in which said pH adjusting agents are selected from the groupconsisting of NaOH, KOH, Ca(OH)₂, Na₂CO₃ and K₂CO₃.
 31. An on-linemethod of simultaneously cleaning and disinfecting an industrial watersystem comprising the steps of: a) providing an industrial water system;wherein said industrial water system is selected from the groupconsisting of cooling water systems and boiler water systems; b)optionally reducing the cycles of said industrial water system to singlecycles and halting the feeding of the routine water maintenancechemicals to the water of the industrial water system. c) adding aCompound selected from the group consisting of the alkali salts ofchlorite and chlorate, or a mixture thereof, and optionally adding acorrosion inhibitor and optionally adding a dispersant to the water ofsaid industrial water system; wherein enough Compound is added to reacha concentration of from about 1 ppm to about 1000 ppm, wherein if acorrosion inhibitor is added enough corrosion inhibitor is added toreach a concentration of from about 50 ppm to about 500 ppm and whereinif a dispersant is added enough dispersant is added to reach aconcentration of from about 1 ppm to about 500 ppm; d) lowering the pHof the water in the industrial water system to about 4.0 by adding anacid to the water of said industrial water system and maintaining the pHof the water in the industrial water system at about 4.0 for from about1 to about 4 hours; e) adding a chelating agent to the water of theindustrial water system, wherein enough chelating agent is added tomaintain the concentration of the chelating agent at from about 10 ppmto about 500 ppm in the water of the industrial water system; whereinsaid chelating agent is added either before or after the optional nextstep of raising the pH; f) optionally raising the pH of the water in theindustrial water system from about 5.5 to about 11 by either addingcaustic or stopping the addition of acid or by a combination of both ofthese methods; g) adding a biocide to the water of the industrial watersystem; wherein if the chelating agent is added after the optional stepof raising the pH, then the chelating agent and the biocide from step g)may be added simultaneously to the water or the chelating agent may beadded first followed by the biocide or the biocide may be added first,followed by the chelating agent; wherein the amount of biocide added isthat amount sufficient to have a concentration of from about 1 ppm toabout 500 ppm in the water of the industrial water system; h) allowingthe water in the industrial water system to circulate for an additionaltime period of from about 1 hour to about 120 hours; and i) concludingthe cleaning and disinfecting method when the desired cleaningefficiency has been achieved; wherein, if feeding of the routine watertreatment maintenance chemicals was stopped during the process, then nowresuming the feeding of the routine water treatment maintenancechemicals to the water of the industrial water system; and wherein iffeeding of the routine water treatment maintenance chemicals was notstopped during the procedure, then now bringing the industrial watersystem back to normal operation by stopping cleaning chemical feed,blowing down the water to reduce system cycles to a single cycle, andthen proceeding under normal operating conditions.
 32. The method ofclaim 31 in which optional step b) is required, and a corrosioninhibitor and dispersant are both added to the water of said industrialwater system.
 33. The method of claim 32 in which said corrosioninhibitor is benzotriazole.
 34. The method of claim 32 in which saiddispersant is a terpolymer comprising from about 30 to about 70 mol %acrylic acid, from about 10 to about 30 mol % acrylamide and from about20 to about 40 mol % aminomethylsulfonic acid.
 35. The method of claim32 in which said Compound is sodium chlorite.
 36. The method of claim 32in which said acid is glycolic acid.
 37. The method of claim 32 in whichsaid chelating agent is sodium hexametaphosphate.
 38. The method ofclaim 32 in which said biocide is 2,2-dibromo-3-nitrilopropionamide. 39.An on-line method of simultaneously cleaning and disinfecting anindustrial water system comprising the steps of: a) providing anindustrial water system; wherein said industrial water system isselected from the group consisting of cooling water systems and boilerwater systems; b) optionally reducing the cycles of said industrialwater system to single cycles and halting the feeding of the routinewater maintenance chemicals to the water of the industrial water system.c) adding a chelating agent to the water of the industrial water system,wherein enough chelating agent is added to maintain the concentration ofthe chelating agent at from about 10 ppm to about 500 ppm in the waterof the industrial water system; wherein said chelating agent is addedeither before or after the optional next step of maintaining the pH; d)optionally maintaining the pH of the water in the industrial watersystem from about 5.5 to about 11 by either adding caustic or stoppingthe addition of acid or by a combination of both of these methods; e)adding a biocide to the water of the industrial water system; wherein ifthe chelating agent is added after the optional step of maintaining thepH, then the chelating agent and the biocide from step e) may be addedsimultaneously to the water or the chelating agent may be added firstfollowed by the biocide or the biocide may be added first, followed bythe chelating agent; wherein the amount of biocide added is that amountsufficient to have a concentration of from about 1 ppm to about 500 ppmin the water of the industrial water system; f) allowing the water inthe industrial water system to circulate for an additional time periodof from about 1 hour to about 120 hours; and g) concluding the cleaningand disinfecting method when the desired cleaning efficiency has beenachieved; wherein, if feeding of the routine water treatment maintenancechemicals was stopped during the process, then now resuming the feedingof the routine water treatment maintenance chemicals to the water of theindustrial water system; and wherein if feeding of the routine watertreatment maintenance chemicals was not stopped during the procedure,then now bringing the industrial water system back to normal operationby stopping cleaning chemical feed, blowing down the water to reducesystem cycles to a single cycle, and then proceeding under normaloperating conditions.
 40. The method of claim 39 in which optional stepb) is required.
 41. The method of claim 39 in which said chelating agentis sodium hexametaphosphate.
 42. The method of claim 39 in which saidbiocide is 2,2-dibromo-3-nitrilopropionamide.